Because the distance between the notes is either a Tone or a semi-Tone, the interval 'pattern' changes depending on which note you start from.

The table below demonstrates the pattern of intervals in the key of C. Note that the pattern is the same for EVERY key.

C

1

2

3

4

5

6

7

Dm

1

2

b3

4

5

6

b7

Em

1

b2

b3

4

5

b6

b7

F

1

2

3

#4

5

6

7

G

1

2

3

4

5

6

b7

Am

1

2

b3

4

5

b6

b7

Bdim

1

b2

b3

4

b5

b6

b7

Spot the difference

Now the intervals have been mapped out, you can spot differences between them. For example:

If I was to play the D minor chord from the C Major scale, then that would include a 6

If I was to play the A minor chord from the C Major scale, then that would include a b6

If I was to play the E minor chord from the C Major scale, then that would include a b6 and a b2

The b2 is a really distinctive sound, so let us assume you would recognise that sound. Let us also assume it might be less common than the othr two minor chords.

Now we have a clear distinction. The D minor has a 6. The A minor has a b6.

What Does this Mean?

If you play a minor chord and it sounds great with a 6, then you are playing the minor chord that is in the '2nd' slot, like D minor is in the C Major Scale.

If you play a minor chord and it sounds great with a b6, then you are playing the minor chord that is in the '6th' slot, like A minor is in the C Major Scale.

If you play a minor chord and it sounds great with a b6, but sounds even better by adding the b2, then you are playing the minor chord that is in the '3rd' slot, like E minor is in the C Major Scale.

You can see differences with the Major chords, too.

Check out the chord from the 4th slot ie F in the C Major Scale. It contains a #4. There is only one place where you get a #4.

Every time you play a Major chord and it sounds great with a #4 then you are playing the 4th chord from the Major Scale.

Every time you play a Major chord and it sounds great with a b7 then you are playing the 5th chord from the Major Scale.

Every time you play a Major chord and it sounds great with no # and no b then you are playing the 1st chord from the Major Scale.

Order, Order!

So I might have a go at putting them in order of how they change. This might be subjective, if so, do it yourself, see what makes sense to you.

Major Chords in order of changes to intervals

C

1

2

3

4

5

6

7

G

1

2

3

4

5

6

b7

F

1

2

3

#4

5

6

7

Minor Chords in order of changes to intervals

Dm

1

2

b3

4

5

6

b7

Am

1

2

b3

4

5

b6

b7

Em

1

b2

b3

4

5

b6

b7

Bdim

1

b2

b3

4

b5

b6

b7

What Now?

Now you need to strum a chord for a while, and see what note sounds good to you. It depends on the vibe you have in mind. It depends upon the sounds and styles of music you like. It just depends. What do you like? I bet you are not too keen on the #4, but think the b7 sounds cool, right?

Now play a song you know, that has only a few chords (K.I.S.S.). Try and see what works over each major chord, is it with a b7, a #4 etc....

You can use that info to find what key you are in based on where that chord slots in to the Major Scale.